CVE-2017-5977 in ZZIPlib
Summary
by MITRE
The zzip_mem_entry_extra_block function in memdisk.c in zziplib 0.13.62 allows remote attackers to cause a denial of service (invalid memory read and crash) via a crafted ZIP file.
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Analysis
by VulDB Data Team • 07/10/2025
The vulnerability identified as CVE-2017-5977 resides within the zziplib library version 0.13.62, specifically in the zzip_mem_entry_extra_block function located in memdisk.c. This flaw represents a classic buffer over-read condition that manifests when processing malformed ZIP archive files. The issue occurs during the parsing of extra field data within ZIP file entries, where the library fails to properly validate the length of extra data blocks before attempting to read from memory locations beyond the allocated buffer boundaries. Such improper validation creates an environment where maliciously crafted ZIP files can trigger invalid memory access patterns, leading to application crashes and potential system instability.
From a technical perspective, this vulnerability operates as a memory safety issue classified under CWE-125, which describes out-of-bounds read conditions. The flaw demonstrates how insufficient input validation can lead to arbitrary memory access patterns that bypass normal program execution flow. When the zzip_mem_entry_extra_block function processes a crafted ZIP file, it attempts to read extra block data without verifying that the requested memory offsets remain within the bounds of the allocated buffer space. This condition creates a scenario where the program may attempt to read from memory addresses that are either uninitialized, unmapped, or otherwise inaccessible, resulting in segmentation faults or access violations that terminate the application process.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited by remote attackers to disrupt services that depend on zziplib for ZIP file processing. Systems utilizing this library for decompression, archive extraction, or file validation purposes become susceptible to crash conditions that can be triggered through various attack vectors including web applications, email systems, or file processing services. The vulnerability is particularly concerning in environments where automated file processing occurs, as a single malicious ZIP file can cause cascading failures across multiple services. Network-based exploitation becomes feasible when the affected applications process user-uploaded content or receive ZIP files from untrusted sources without proper sanitization.
Mitigation strategies for CVE-2017-5977 should focus on immediate library updates to versions that contain patched implementations of the zzip_mem_entry_extra_block function. System administrators must prioritize patching affected applications that rely on zziplib, particularly those handling untrusted ZIP file inputs. Input validation measures should be implemented at multiple layers, including pre-processing checks that verify ZIP file structure integrity before passing files to the zziplib library. Additionally, deployment of intrusion detection systems capable of identifying malformed ZIP file patterns and network-based filtering rules that can block suspicious file transfers represent effective defensive measures. The vulnerability also highlights the importance of implementing proper memory safety practices in C/C++ applications, including the use of modern compiler flags and static analysis tools that can identify similar buffer over-read conditions. Organizations should consider implementing sandboxing techniques for file processing operations and establishing robust monitoring procedures to detect potential exploitation attempts targeting this class of vulnerabilities.